Property and Equipment - Tabular Disclosure of Major Components of Property and Equipment and Related Accumulated Depreciation (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Property Plant And Equipment [Abstract]
Leasehold improvements	$ 525	$ 525
Laboratory equipment and other	2,850	2,856
Total property and equipment, at cost	3,375	3,381
Less: accumulated depreciation	3,259	3,163
Property and equipment, net	$ 116	$ 218